A vegan activist has told a heartbroken dairy farmer crying about her family having to give up their farm that she should 'get another job'.

Casey Treloar, 26, shared an emotional video revealing her sadness at her family having to give up the farm they had owned for 40 years in Flerieu Peninsula, South Australia on Sunday.

In response, vegan Joey Carbstrong, 32, posted a video to YouTube telling Ms Treloar and her family to deal with what he claimed was a decreasing demand for dairy products, saying the industry was an 'injustice'.

Casey Treloar (pictured), 26, shared an emotional video revealing her sadness at her family having to give up the farm they had owned for 40 years

In response, vegan Joey Carbstrong (pictured), 32, posted a video to YouTube telling Ms Treloar and her family to deal with what he said was decreasing demand for dairy products

'What I found interesting is that she considered herself a cow person. Which is really, really bizarre seeing as all those cows go to the slaughterhouse, the bobby (newborn) calves are all killed, they're all taken away from their mothers, it's a horrifically cruel and abusive industry,' Mr Carbstrong said.

He claimed Ms Treloar was 'indoctrinated by dairy farming'.

'I mean it's been passed down traditionally, she said her father did it, her father's father probably did it too. Something she considers normal... but what's happening is demand is changing because we demand you release these animals and stop breeding them into existence to exploit them,' he said.

'It's time to move into plant-based alternatives... Why don't you just move industries? You're going to have to move industries eventually because dairy is going to become obselete.

The Australian dairy industry is concentrated in the south-east of Australia, Victoria is the largest production state, however other states have significant dairy industries.

Victorian production is typically seasonal and enters the export market which makes it prone to volatile global prices. Other dairy production areas (i.e. much of NSW) supply the domestic market which requires year-round production.

The dairy industry is heavily reliant upon water availability; the industry is currently facing uncertainty over water policy.

Since deregulation in 2001, the industry has undergone rationalisation. This has left a core of efficient producers that are able to compete against international competitors who are heavily subsidised.

Source: PWC's The Australian Dairy Industry report

Ms Treloar, who is a third-generation dairy farmer in South Australia, was brought to tears as she said farewell to the industry she has grown up in.

'The clock has run out and it's time to say goodbye,' she said.

'We are getting 38 cents a litre across the year and it's completely unsustainable. We can't really afford to keep going anymore.

'We're forever the optimist that the industry will get better - but for our family, we've come to a point where we can't do it anymore.

'Dairying is something my dad has done his entire life, and I have done my entire life, but it has come to the point where our family has had to say ''that's it for us''.'

She said her family's product had been devalued by dollar-a-litre milk, which had added to the problems facing the industry.

Supermarket giants Woolworths and Coles decided in 2010 to sell milk for a dollar a litre, sparking a sharp cut to the viability of farming dairy.

Dairy farmers have hit back ever since, claiming the price drop was devastating the industry.

Australia is the world's third-largest dairy exporter, with 50 per cent of production sent overseas.

The dairy industry is worth $4billion to the Australian economy. Australia produces a range of dairy products including milk, milk powder, yoghurt, butter and cheese.